Fix const correctness of containerForRepaint

Source/core/rendering/RenderObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 795 matching lines @@
         Color color;
         TextDecorationStyle style;
         AppliedTextDecoration() : color(Color::transparent), style(TextDecorationStyleSolid) { }
     };
 
     void getTextDecorations(unsigned decorations, AppliedTextDecoration& underline, AppliedTextDecoration& overline, AppliedTextDecoration& linethrough, bool quirksMode = false, bool firstlineStyle = false);
 
     // Return the RenderLayerModelObject in the container chain which is responsible for painting this object, or 0
     // if painting is root-relative. This is the container that should be passed to the 'forRepaint'
     // methods.
-    RenderLayerModelObject* containerForRepaint() const;
+    const RenderLayerModelObject* containerForRepaint() const;
 
     // Actually do the repaint of rect r for this object which has been computed in the coordinate space
     // of repaintContainer. If repaintContainer is 0, repaint via the view.
     void repaintUsingContainer(const RenderLayerModelObject* repaintContainer, const IntRect&, InvalidationReason) const;
 
     // Repaint the entire object.  Called when, e.g., the color of a border changes, or when a border
     // style changes.
     void repaint() const;
 
     // Repaint a specific subrectangle within a given object.  The rect |r| is in the object's coordinate space.
@@ skipping 634 matching lines @@
 void showTree(const WebCore::RenderObject*);
 void showLineTree(const WebCore::RenderObject*);
 void showRenderTree(const WebCore::RenderObject* object1);
 // We don't make object2 an optional parameter so that showRenderTree
 // can be called from gdb easily.
 void showRenderTree(const WebCore::RenderObject* object1, const WebCore::RenderObject* object2);
 
 #endif
 
 #endif // RenderObject_h